Recently, various types of an electronic apparatus such as a tablet computer and a notebook personal computer (PC) have been developed. Many of these types of an electronic apparatus have various power saving control functions for reducing a power consumption of the electronic apparatus. A function for shifting an electronic apparatus to a hibernation state or to a suspend state has been known as one of typical power saving control functions.
In the hibernation state, power of almost all the components in an electronic apparatus is turned off in a state that a system context is stored in a non-volatile storage. In this way, placing the electronic apparatus in the hibernation state while it is in an idling state and the like can reduce power uselessly consumed by the electronic apparatus.
In the stand-by state, power of almost all the components except a main memory is turned off. Thus, the stand-by state is also useful to reduce useless power.
Further, a recent electronic apparatus uses also a function for shifting devices in the electronic apparatus to a power saving mode.
Since power saving is required in view of recent social conditions, much of an electronic apparatus in an office and the like is operated in such a manner that a hibernation state or a stand-by state is frequently used.
However, ordinarily, when an electronic apparatus returns from the hibernation state or the stand-by state to a working state, almost all the devices in an electronic apparatus are reset to an ordinary operating state. Accordingly, the electronic device may consume a relatively large amount of power for some time after it has returned to a working state.